gdb.ada/maint_with_ada.exp: New testcase

gdb.ada/maint_with_ada.exp: New testcase

This commit adds a new testcase testing the "check-psymtabs" and
"check-symtabs" maintenance commands.

The "maintenance check-psymtabs" commands is currently known to
produce some errors. While the situation was admetedly made worse
by the following patch...

    commit b5ec771e60c1a0863e51eb491c85c674097e9e13
    Date:   Wed Nov 8 14:22:32 2017 +0000
    Subject: Introduce lookup_name_info and generalize Ada's FULL/WILD name matching

... hence the reference to PR gdb/22670, the command was already
spotting one inconsistency prior to it:

    (gdb) maintenance check-psymtabs
    Global symbol `interfaces__cS' only found in /[...]/b~var_arr_typedef.adb psymtab

For now, the "check-psymtab" test is KFAIL-ed.

gdb/testsuite/ChangeLog:

        PR gdb/22670
        * gdb.ada/maint_with_ada: New testcase.

Tested on x86_64-linux.